I’d be a liar to say that lessons are often easy to learn – quite the opposite in fact and in particular trying understand the complexity of Human Movement.
Also the reality of previous study having set one up to wrongly believe in therapies, treatments and specific forms of training as being ‘functional’ or to improve ‘performance’. Well we all are continually learning….(are you?).
Take the foot – it’s correct motion can hold the key to function and performance! It’s an amazing design!
In majority of functional movement when we are being driven by gravity, ground reaction force and our own mass and momentum (1) (walk, run, jump, compound lift and active daily living) the foot will be the first point of contact with the surface we’re on and there are key mobility and stability requirements that can dramatically improve or detract from our performance.
First let’s look at some basic anatomy:
Each foot contains: 26 bones (not counting sesamoid and ossicles) – 33 joints
The Key joint that could be described as the ‘Switch’ or ‘Trigger’ is the Subtalar Joint (STJ) as it can switch on/fire an entire chain of events and create increased muscular reaction from a number of muscles and in particular our Gmax!
As you can see it’s the joint between the Talus (proximal bone) and the Calcaneus (distal bone). During weight bearing and in walking as the heel strikes the ground the STJ ‘Switches’ on the kinetic chain both proximal (upwards to the hips and beyond) and distal (through the mid foot and toes).
Proximal Kinetic Chain Reaction of the STJ
On heel strike the STJ will dorsiflex in the sagittal plane, evert in the frontal plane and abduct in the transverse plane with the talus on top internally rotating in the transverse plane causing (due to the ‘mortice’ like talocrural joint) the tibia and fibula to also internally rotate, this will then take the femur into adduction and internal rotation. All this correct motion will ‘load’ our lower limb muscles eccentrically through 3 dimensions in particular our Gmax and develop energy to be used in a concentric ‘unload’ of said muscles.
Distal Kinetic Chain Reaction of the STJ
With the motion of the STJ on heel strike the Mid Tarsal Joint (MTJ) (Where the talus and calcaneus articulate with the navicular and cuboid bones respectively) ‘unlocks’ allowing the medial longitudinal arch to flatten creating a receptive foot to absorb impact and eccentrically ‘load’ our muscles further prior to a concentric ‘unload’.
WHY DO WE NEED STJ MOTION?
In functional movements our muscular system is primarily a reactive system which gets its signals from our nervous system (proprioceptors) to fire muscle groups or not as the case may be. To try and consciously recruit the muscles in their right order of motor patterning in all their complexities would be impossible (2) i.e. kicking a football or picking up your child from the floor.
Therefore we rely on our bones to move correctly (in space) in order for our nervous system to sense the motion at the joints and within the muscles through their eccentric lengthening/loading so the appropriate motor pattern and muscular reaction is initiated with a concentric shortening/unloading to complete the objective movement successfully!
In Summary STJ the Genius!
Having the right amount of motion and stability through the foot and ankle is crucial to function and performance for FOOT SAKE!
Find out how you can assess, analyse and predict the right STJ motion and how to apply exercises to improve its function!
(1) Gray Institute
Gary Gray, Dave Tiberio, Doug Gray
(2) ‘Optimal Movement Variability: A New Theoretical Perspective for Neurologic Physical Therapy’
Nicholas Stergiou, Regina T. Harbourne, James T. Cavanaugh Journal of Neurologic Physical Therapy Vol.30 No.3 2006